When Nick Noonan clicked on his band Karmin’s YouTube page during the day on Thursday, April 14, his jaw dropped. Noonan, a Maine native and 2004 graduate of Old Town High School, couldn’t believe what he was seeing. One million views for a video he and his fiancee and musical partner, Amy Heidemann, uploaded less than 48 hours before. The couple, who live in Boston and have been performing as Karmin for several years, were stunned.

“Amy was getting back to our house, and I ran outside to meet her. We just started jumping around screaming,” said Noonan. “I laid down on the ground in the street. I was just freaking out. It was like winning the lottery.”

Noonan, son of Mike and Judy Noonan of Old Town, and Heidemann, originally from Seward, Neb., are now enjoying their wild ride, which is still going and doesn’t appear to be stopping anytime soon. The video, which is of Karmin covering Chris Brown’s pop hit “Look At Me Now,” had 6.7 million hits on YouTube and was climbing as of the writing of this article.

Pop and hip-hop royalty like Ryan Seacrest, Questlove, Nicki Minaj, Timbaland, Ashton Kutcher, Demi Moore and Jermaine Dupri all have professed their love for the clip. And what’s not to love about it? An adorable girl spitting rapid-fire rhymes and then harmonizing beautifully with a cute, piano-playing boy. Their charm and talent are irresistible.

Heidemann and Noonan met at Berklee College of Music in Boston, and they’ve been virtually inseparable since. Heidemann studied vocal performance at Berklee; Noonan studied trombone, but could sing and play other instruments as well. She had dreams of someday making a career out of singing and performing; he was a lifelong musician, a core member of the jazz program at Leonard Middle School and Old Town High School.

“The whole school system was really supportive of music. My whole family is really supportive of me and what I do. Old Town has one of the best jazz programs in the state. I had some amazing teachers. I was lucky all around,” said Noonan, who cites teachers David Saucier, Shianne Wheeler and Jeffrey A. Priest as inspirations.

Mike and Judy Noonan are as proud and excited as parents could be — though they always knew their son was one talented kid.

“He’s such a happy, positive person, and he really loves what he does. He’s a really lucky kid,” said Judy Noonan. “There’s the possibility that a lot of good things could come from it. In some ways, I’m surprised, and in other ways, I’m not. We always knew he could do it. We’re all extremely excited for him.”

A few years after meeting each other, Heidemann and Noonan decided to make music together, forming Karmin in 2009 and writing songs and performing them all over the East Coast. They released an album in May 2010 called “Inside Out,” featuring their sweet-natured acoustic pop, which can be seen in videos like the one for their song “You Can Tell Me”. Success was moderate, however. They had to take it to the next level.

“The whole idea was to practice, and to raise awareness about us,” said Noonan. “If we did cover songs our way, people would listen and see who we are. It would create a buzz. Then they might check out our original stuff, too.”

Though Heidemann has a clear, expressive pop vocal style, rapping was something she was initially shy about doing, despite knowing she was pretty good at it.

“I had done it in the shower, but I was way too scared to put it in the public eye,” said Heidemann. “I worked my whole life to be a good singer, and that’s what I wanted to be recognized for. But I knew I was good at [rapping]. Nick gave me courage.”

Their videos had some minor success, regularly getting between 6,000 and 7,000 hits within a few weeks of a video being uploaded. People responded to their effortless chemistry and undeniable musical skill, but a big viral hit had eluded them. On Tuesday, April 12, the pair uploaded their version of Chris Brown’s “Look At Me Now,” a song that features extremely fast-paced rapping, which Heidemann replicates perfectly. That’s when the craziness began.

“On the first day, we got around 13,000 views. We thought, ‘Wow, that’s a lot.’ We had a couple that got six or seven, but never 13,” said Noonan. “Then it started getting retweeted. Then it got picked up on Reddit. Then it got picked up by World Star Hip Hop, which is this huge website that millions of people that love hip-hop visit all the time. We were shocked. Two white kids from Maine and Nebraska got 250,000 views on YouTube because of that.”

That was only the beginning. Questlove, the drummer from the Roots, tweeted “Look At Me Now.” Then Ryan Seacrest tweeted it. Then Nicki Minaj tweeted it.

“The water broke, and within 48 hours, we had over a million hits. I hadn’t even had a chance to call my parents before Ryan Seacrest Tweeted it,” said Noonan. “And what was even better was that we had all these videos we’d already posted, so people could watch those too. They all got a huge boost.”

“Last Thursday and Friday were two of the craziest days of our lives,” said Noonan. “We weren’t ready for that kind of attention. Labels and producers started reaching out. It was just unbelievable. Two weeks have seemed like one day. I still can’t believe it’s happening.”

On Friday, April 15, they got a call from the producers of “Ellen,” expressing possible interest on having Karmin on the show the next week. Despite no guarantees, Noonan and Heidemann packed their bags and flew to Los Angeles on April 16. They appeared on “Ellen” on April 20, performing “Look At Me Now” and an original, “On Your Side,” and they got to meet Portia DeRossi and Justin Timberlake backstage.

They also have been in meetings all week. Kara DioGuardi, formerly of “American Idol,” expressed interest; even Jimmy Iovine, president of Interscope Records, has heard their music.

“Everyone’s coming out swinging for us,” said Noonan. “Our original stuff is a lot lighter and more pop-influenced, though the hip-hop influence has been creeping in. Whatever we end up doing, wherever we end up signing, we want to make sure we can keep doing what we love. We don’t want the most money. We just want to be able to make the music we love.”

The pair returned to the East Coast on Wednesday, after 11 days in Los Angeles. They’ll have a second or two to breathe, before part two of the Karmin adventure begins. Hopefully they’ll be able to visit all their family and friends in Old Town. At the very least, they’ll have a little time off to get married on Sept. 10.

“We’re getting married on 9-10-11. We’re having a small, low-key wedding in my backyard in Nebraska, Forrest Gump style,” said Heidemann. “We were originally going to get married and then drive to LA from Nebraska. I think it might be a little bit different now.”